sched/core: Fix an SMP ordering race in try_to_wake_up() vs. schedule()

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / kernel / trace / trace_kprobe.c

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 9f46e98ba8f22a712962ccc68e17b34f166439ba..64abc8ca928b3da7d0b78ab3811695b49f2e8c1c 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -90,7 +90,7 @@ static __kprobes bool trace_probe_is_on_module(struct trace_probe *tp)
 }
 
 static int register_probe_event(struct trace_probe *tp);
-static void unregister_probe_event(struct trace_probe *tp);
+static int unregister_probe_event(struct trace_probe *tp);
 
 static DEFINE_MUTEX(probe_lock);
 static LIST_HEAD(probe_list);
@@ -281,6 +281,8 @@ trace_probe_file_index(struct trace_probe *tp, struct ftrace_event_file *file)
 static int
 disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
 {
+       struct ftrace_event_file **old = NULL;
+       int wait = 0;
        int ret = 0;
 
        mutex_lock(&probe_enable_lock);
@@ -314,10 +316,7 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
                }
 
                rcu_assign_pointer(tp->files, new);
-
-               /* Make sure the probe is done with old files */
-               synchronize_sched();
-               kfree(old);
+               wait = 1;
        } else
                tp->flags &= ~TP_FLAG_PROFILE;
 
@@ -326,11 +325,25 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
                        disable_kretprobe(&tp->rp);
                else
                        disable_kprobe(&tp->rp.kp);
+               wait = 1;
        }
 
  out_unlock:
        mutex_unlock(&probe_enable_lock);
 
+       if (wait) {
+               /*
+                * Synchronize with kprobe_trace_func/kretprobe_trace_func
+                * to ensure disabled (all running handlers are finished).
+                * This is not only for kfree(), but also the caller,
+                * trace_remove_event_call() supposes it for releasing
+                * event_call related objects, which will be accessed in
+                * the kprobe_trace_func/kretprobe_trace_func.
+                */
+               synchronize_sched();
+               kfree(old);     /* Ignored if link == NULL */
+       }
+
        return ret;
 }
 
@@ -398,9 +411,12 @@ static int unregister_trace_probe(struct trace_probe *tp)
        if (trace_probe_is_enabled(tp))
                return -EBUSY;
 
+       /* Will fail if probe is being used by ftrace or perf */
+       if (unregister_probe_event(tp))
+               return -EBUSY;
+
        __unregister_trace_probe(tp);
        list_del(&tp->list);
-       unregister_probe_event(tp);
 
        return 0;
 }
@@ -679,7 +695,9 @@ static int release_all_trace_probes(void)
        /* TODO: Use batch unregistration */
        while (!list_empty(&probe_list)) {
                tp = list_entry(probe_list.next, struct trace_probe, list);
-               unregister_trace_probe(tp);
+               ret = unregister_trace_probe(tp);
+               if (ret)
+                       goto end;
                free_trace_probe(tp);
        }
 
@@ -1312,11 +1330,15 @@ static int register_probe_event(struct trace_probe *tp)
        return ret;
 }
 
-static void unregister_probe_event(struct trace_probe *tp)
+static int unregister_probe_event(struct trace_probe *tp)
 {
+       int ret;
+
        /* tp->event is unregistered in trace_remove_event_call() */
-       trace_remove_event_call(&tp->call);
-       kfree(tp->call.print_fmt);
+       ret = trace_remove_event_call(&tp->call);
+       if (!ret)
+               kfree(tp->call.print_fmt);
+       return ret;
 }
 
 /* Make a debugfs interface for controlling probe points */